GIS专业基于面向对象程序设计的DEM生成教学实验设计

数字高程模型是地理信息科学专业的必修课,DEM生成方法是该课程的核心知识点之一。通常以GIS软件为实验操作平台构建DEM,GIS软件提供良好的操作界面且简化教学过程,但软件同时会弱化学生对DEM生成过程的理解,而面向对象程序设计课程往往开设在数字高程模型课程之前。文中融合面向对象程序设计和数字高程模型课程知识点,采用面向对象程序设计思想对DEM课程中的DEM生成实验进行设计并实现,为GIS专业的DEM生成实验提供新的教学思路,提升DEM课程教学实践的品质和效果。     

Delaunay三角网的并行构网算法

针对传统的Delaunay三角网的并行构建算法负载均衡性不高、运行效率较低等问题,该文在综合逐点插入算法和分治算法各自优点的基础上,提出了一种Delaunay三角网并行构建算法。该算法首先使用动态格网剖分点要素集,从而得到若干点要素子集;然后根据点要素子集数量初始化线程池,每个点要素子集由一个线程按照插入点法构建Delaunay子网;当所有线程完成子三角网构建,最后使用逐点插入法合并所有子网,从而实现所有点要素的Delaunay三角网构建。分析与实验结果表明,相对于传统的并行算法,该并行算法的负载均衡性好、运行时间少、加速比高,具有较好的构建效率,而且构建结果满足Delaunay规则。     

Calibrating a Land Parcel Cellular Automaton (LP-CA) for urban growth simulation based on ensemble learning

The reliability of raster cellular automaton (CA) models for fine-scale land change simulations has been increasingly questioned, because regular pixels/grids cannot precisely represent irregular geographical entities and their interactions. Vector CA models can address these deficiencies due to the ability of the vector data structure to represent realistic urban entities. This study presents a new land parcel cellular automaton (LP-CA) model for simulating urban land changes. The innovation of this model is the use of ensemble learning method for automatic calibration. The proposed model is applied in Shenzhen, China. The experimental results indicate that bagging-Naïve Bayes yields the highest calibration accuracy among a set of selected classifiers. The assessment of neighborhood sensitivity suggests that the LP-CA model achieves the highest simulation accuracy with neighbor radius r = 2. The calibrated LP-CA is used to project future urban land use changes in Shenzhen, and the results are found to be consistent with those specified in the official city plan.     

不规则伊/蒙混层粘土矿物成因类型及晶体化学分类

不规则伊/蒙混层粘土矿物(I/S)分布极为广泛,根据大量资料,提出了I/S的成因及晶体化学分类。按其成因分为三类:成岩型、风化型、火山热液型;按其晶体化学性质分为完全无序型、部分有序型及准晶态型。讨论了各成因类型I/S的晶体化学特点,认为产出于P/T界线层粘土中的I/S具二维晶格一维准晶格。探讨了I/S与烃类形成的关系。     

Isoprenoid alkanes with irregular “head-to-head” linkages

A lightly biodegraded crude oil from the Tolkinsk field (Upper Jurassic), situated in north-west Siberia, was found to contain a series of C₂₈–C₃₉ isoprenoid alkanes. Most of these components contain a pristane unit linked head-to-head with other isoprenoid units. The structures of these components were elucidated by mass spectral interpretations, comparisons with a synthesised standard and by reference to data published previously in the literature. These results extend the carbon number range, the variety of structural types, and the number of reported occurrences of these compounds in geological samples. These results provide further evidence for a contribution of bacterial cell-wall lipids to crude oils.     

Light curve behaviour in C/1995 O1 (Hale-Bopp) — II

Comet Hale-Bopp is, without doubt, one of the most important objects for cometary science which has ever been observed. The light curve is well-observed from a heliocentric distance 7.2 AU and some information is available at distances as great as 17 AU. This allows the photometric evolution of the comet to be studied as different volatiles dominate the activity. Three different phases of activity are seen as the heliocentric distance reduces during 1996: the initial phase of very fast brightening, characterized by a r ^–5 law; a standstill in the light curve when the brightening law reduced to r ^–1, which coincides with the initiation of water sublimation at r ~ 4 AU; and a further phase of more rapid brightening with an r ^–3.5 law, similar to the mean for comets classed as fairly new, which initiated at r ~ 4 AU.     

Early Holocene shore displacement and evidence of irregular isostatic uplift northwest of Lake Vänern, western Sweden

In the 1920's the Swedish geologist Lennart von Post found evidence of irregular early Holocene isostatic uplift in the region northwest of Lake Vänern in western Sweden. von Post based his conclusions on levellings of ancient shore lines. These were indirectly dated by pollen stratigraphical investigations in basins situated at approximately the same altitudes as the shore lines. To test von Post's hypothesis, we have adopted a different methodological approach. The sediments in twelve small lake basins, within five minor areas in this region, have been investigated with respect to when they became isolated from ancient Lake Vänern. Initially all the lake thresholds were levelled. Altitudes range between 165 and 96 m above sea level. By combining the results of mineral magnetic and diatom stratigraphical analyses it has been possible to determine the level in the sediment when the basin became isolated. The ¹⁴C age of this isolation level has been inferred from AMS dates based on the NaOH-soluble fraction of bulk sediment, partly with very low organic content. Altogether, 36 radiocarbon datings have been carried out, ranging from 10080 to 8800 ¹⁴C years BP. Pollen analyses, and subsequent correspondence analysis (CA) of all pollen spectra, were carried out around the isolation level in each basin as a complement to the AMS datings.If the region had been subject to irregular isostatic uplift, lakes at the same altitude in the five areas should have been isolated at different times. The AMS determined isolation ages, corrected according to CA of the pollen stratigraphy and compensated for the relatively higher rebound of the northerly situated sites support von Post's conclusion, from the beginning of this century, that the region northwest of Lake Vänern has been subjected to irregular isostatic uplift.     

全空间信息系统的核心问题和关键技术

分析了空间信息系统的研究现状和存在问题,阐明了全空间信息系统的基本概念和基本特征;提出了基于多粒度时空对象构建全空间信息系统的技术路线,明确了需要研究解决的科学问题和关键技术;提出了全空间信息系统与智能设施管理的主要研究内容,指出预期的研究效益。     

Modeling spatiotemporal topological relationships between moving object trajectories along road networks based on region connection calculus

Considering the attempts to model spatiotemporal topological relationships between moving object trajectories, the conceptual and computational framework for moving objects along a road network has not received much attention. This paper aims to draw an improved model based on Region Connection Calculus (RCC) theory to represent the spatiotemporal topological relationships between moving object trajectories along road networks. This paper first uses a dimension reduction method based on a linear-reference transformation to model the moving object trajectories segments, and then defines new time–connection and space–connection relations between two trajectory segments. On this basis, the paper proposes an extension to the RCC-based spatiotemporal binary relationship set so that the combined semantics of the spatiotemporal predicates can be described completely. A case study was carried out using Floating Car Data in Guangzhou city. The computational results show that in a real application, the occurrence frequencies of the RCC-based binary relationships are distributed nonuniformly and the semantics of some binary relationships with the highest occurrence are coarse. Therefore, the partition of the spatiotemporal connection relations and the finer aspects of the spatiotemporal relationship model may require further research work.     

基于三维激光扫描技术的不规则物体表面积的测定方法

采用三维激光扫描技术可以快速获取物体表面的三维信息。对包含这些三维信息的点云进行处理能够获得广泛的应用。本文介绍了三维激光扫描仪的原理,并对其进行表面积计算和可行性研究,并在实际测量中进行应用。经验证采用三维激光扫描技术可以高精度、快速、便捷地实现不规则物体表面积的计算。